[Bookmark] Add bookmark module

- Remove all torrents of the current category. Fix #62
- Add 15 first torrents to Autoget (autoget is limited to 15 torrents). Fix #61
- Optionaly delete torrents added to Autoget from bookmarks.
- Add an option to torrent_list to bookmark first 40 torrents (bookmarks are limited to 40/category)
- Add a global utils.multiGet funtion helper for multiple ajax request to /ajax.php (needed for previous functions, see those for usage exemple)